Updates references to SimpleNodeParser to SentenceSplitter. (#1129)

apps/docs/docs/modules/ingestion_pipeline/index.md

apps/docs/docs/modules/ingestion_pipeline/transformations.md

apps/docs/docs/modules/node_parser.md

apps/docs/docs/modules/query_engines/router_query_engine.md

examples/agent/multi_document_agent.ts

examples/extractors/keywordExtractor.ts

examples/extractors/questionsAnsweredExtractor.ts

examples/extractors/summaryExtractor.ts

examples/extractors/titleExtractor.ts

examples/jupyter/nodeparser.ipynb

examples/lowlevel.ts

examples/pipeline/ingestion.ts

examples/routerQueryEngine.ts

examples/summaryIndex.ts

packages/llamaindex/tests/MetadataExtractors.test.ts

packages/llamaindex/tests/ingestion/IngestionCache.test.ts